What's the most obviously satirical website to be widely taken at face value?

That site’s a spoof. The International Flat Earth Society was a real organisation, albeit with only one active member since the 60s, Charles Johnson, who died in 2001. There’s loads of spoof sites now. Plus a heavy metal band going by that name, it seems.

Actually, I don’t think their website will take anyone in, but before they had it I’ll bet a lot of people though Hiney Wines was for real:

http://www.hiney.com/

How the hell are you supposed to know, when Bootie Beer is for real?

(It’s horrible, BTW. Slave to advertising and good product naming that I am, I had to try it. Apparently the Light version is a bit better)

I believe His4ever was once whooshed by the same article, then tried to claim, “well, it COULD be true.”

The amputee wannabe website (now gone) had a few people going. Here’s the main story from the site
Re great sites where the hell did www.manbeef.com go? Site’s gone!

Astro, as far as anyone can tell, that chick really DID want to be a double amputee. The made-up part where she actually went through with it - call it a Mary-Sue fanfic, maybe. But the site wasn’t an intentional spoof.

I too, miss ManBeef. That was a GOOD one.

Yeah, because I was just going to say that Jane magazine ran a story featuring a woman who fantasized about being an amputee, and “lived out” her fantasy by sitting in front of mirrors so that it looked like she was missing a leg. She even applied tourniquets from time to time. Apparently these people are real. Like furries.

http://www.gatt.org/ made by http://theyesmen.org/

I’d say the 2001 incident where radical Islamic protesters carried Evil Bert pictures is the biggest and most bizarre whoosh to date.

As Snopes explains, it was a blunder by a print shop in Dhaka, Bangladesh, not an intentional statement of ideology. It’s still hilarious.